Pads for supporting rails



Feb. 20, 1968 I E. o so 3,369,753

PADS FOR SUPPORTING RAILS Filed Sept. 2, 1966 United States Patent ABSTRACT OF THE DISCLOSURE A resilient (i.e. compressible), wedge shaped pad is interposed between a rail and a sleeper for the latter and in supporting relationship to the rail so that the rail is normally disposed at an inclination relative to the vertical. The pad is provided with means, such as wall structure defining a cavity or a plurality of grooves, at the thickest portion of the pad, so that the latter is rendered more compressible at such portion than at the opposite portion thereof. Thus, when normal working forces are applied to the rail, the more compressible portion will be compressed to a greater extent and the rail will be rotated r about its horizontal axis.

The utilization of concrete sleepers for railway purposes has increased greatly in the recent years. A concrete sleeper has about the double length of life as compared with a high quality wooden sleeper under similar working conditions. A constructional difiiculty in connection with concrete sleepers has been to connect the rail to the sleeper in such way that a permanent connection is secured which is free of maintenance for a plurality of years, and also suflicient resiliency in lateral and vertical direction is obtained. For illustrating the complicated nature of the problem it can be mentioned that in connection with concrete sleepers which are manufactured in amounts of several millions, it has been necessary to provide wooden dowels in the pretensioned concrete for mounting the rail fastener device by means of this joint member so that the risk of cracking is reduced.

For sleepers which are adapted to be laid in'straight tracks, the different rail fastener devices which have been developed, usually could be made with sufiicient length of life with respect to their mechanical characteristics and cooperation with the concrete, although certain of these well-known rail fastener devices have caused a substantial maintenance work due to the adjustment of some elements forming parts of the fastener device. Yet, resilient fastener devices have been developed which are completely free of maintenance and have no such parts which require adjustment. In straight tracks the lateral forces are naturally lower than in curves and therefore these forces generally could be taken up by friction in the concrete surface and/or by tensile and bending strains in fastener means inserted in the concrete, without any cracking of the concrete.

However, in curved tracks the lateral forces increase substantially, and the impact action on the concrete through fastener elements moulded in the concrete is often destroying. The single solution of the problem, that as far as known has been tried successfully, constitutes therein that the rail is mounted in a steel plate, which is recessed I in the concrete and which through its much greater surface transfers the forces to the concrete via a flat thin rubber plate. The reason for this construction is that the friction between rubber pad and concrete surface that can be fully utilized, is alone not sufiicient -for taking up the lateral forces. However, a recess in the concrete directly below the rail will mean a weakening of the crosssection of the concrete in the part subjected to the highest stresses, and the affect of the same can grow still worse if for some reason a direct contact occurs between the steel plate or the rail and the edge of the concrete, which in such a case is worn off. A general weak point which also is inherent in the well known fastener devices, is that these devices tend to lock the rail to the sleeper without definable lateral spring conditions.

The present invention has for its object to avoid the disadvantages set forth above.

Previously the knowledge of the dynamic forces and the investigations of the quantitative distribution have been of limited scope. Through empirical studies recently made by the inventor it has been shown that the maximum lateral forces determining the dimensions of the rail fastener devices on a sleeper as a rule are always oppositely directed inasmuch as the lateral force on the inner rail of a curvedtrack is directed inwards, thus opposite to the centrifugal force.

This ascertainment has according to the invention been utilized in such way that the interconnection of rail and sleeper has been made by the aid of resilient (i.e. compressible) plates supporting the rail, said resilient pad allowing a rotation of the rail around its longitudinal axis when subject to vertical and horizontal forces, and having a thickness increasing like a wedge towards the outer side of the rail of the track.

Accordingly, it is essential that the rail when subject not only to vertical forces but also to horizontal forces, has the possibility of performing a controlled rotation around its longitudinal axis before the resultant of the horizontal force and the vertical force falls outside the base of the rail, the pads just on account of its great resiliency and characteristic shape allowing this rotation while simultaneously being subjected to a lateral shearing strain, Hereby, the horizontal force acting at the rail base is distributed over a plurality of sleepers and is counteracted not only by pure horizontal forces but also by torsional forces having a longitudinal axis of moment.

Embodiments of a rail supporting pad according to the invention are by way of example illustrated diagrammatically in the accompanying drawing, in which FIGS. 1, 2 and 3 are cross-sectional views of the pad with adjacent part of the sleeper, taken transversely to the longitudinal direction of the rail.

In FIG. 1, the reference numeral 1 indicates the rail supporting pad which consists of a material with a relatively great resiliency, such as vulcanized rubber or a similar plastic or the like, 2 is the adjacent part of the rail base and 3 is the adjacent part of the concrete sleeper. The outer edge of the rail, viz. the edge facing outwards from the track, lies to the left in the figure, and the thickness of the pad 1 increases like a wedge towards said edge. The resiliency (i.e. compressibility) of the pad 1 is so great that it allows a tilting movement of the top surface of the pad, for instance of the order of 1 millimetre at the outer edge, as well as a lateral shear movement, both movements with controlled restoring forces. Furthermore, the reference numeral 4 indicates the rail fastener device, by means of which the rail is clamped against the pad 1 and thereby against the sleeper 3. The rail fastener device 4 can be made as a loop, extending under a peg 5 inserted through the sleeper, and being clamped down wards like a bow over the upper surface of the rail base.

In FIG. 2, the reference numeral 6 indicates a reinforcing and resilient steel plate in the pad, the rubber of the pad being vulcanized to said steel plate, which is bent upwards over the rail base. The steel plate 6 projects from the pad 1 and is bent upwards and inwards over the rail base to such extent that this bent portion constitutes a contact surface for the rail fastener device 4 engaging upon the rail base.

In FIG. 3 the reference numeral 7 indicates rectangular shallow recesses in the bottom surface of the pad, said recesses extending transversely to the sleeper (in the longitudinal direction of the rail) and being provided for engagement with corresponding rectangular low projections on the upper surface of the sleeper. If desired, the recesses 7 in the pad and the corresponding projections on the sleeper can be wave-shaped. It should be observed that for the rest the sleeper has a pure horizontal top surface, and this means that it can be designed lower than the well-known sleepers which have end portions with oblique top surface and large recesses for the rail base, as hitherto usual.

As apparent from FIG. 3, the thicker half portion of the pad 1 can be made so as to be more resilient (Le. compressible) than the remaining portion of the pad, for instance by forming grooves 8 in the upper side or cavities 9 within the material.

The invention is not restricted to the embodiments illustrated and described, modifications being possible within the scope of the appendant claims.

I claim:

1. In a rail support,

an elongated pad of resilient material adapted for interpositioning between a rail and a sleeper for the rail in supporting relationship to the rail, said pad having a first side portion and a second side portion positionable on opposite sides of said rail,

said pad including means positioned in one of said portions to modify the normal compressibility of the pad at said one portion so that the compressibility of said first side portion is substantially greater than the compressibility of said second side portion, said means defining an area in said pad with a different structural character than other areas in said pad,

whereby a rail supported by the pad is rotatable about its longitudinal axis toward said first side portion when subjected to a force placing said pad in compression.

2. A support as set forth in claim 1 wherein said pad is generally transversely wedge shaped and increases in thickness as said first side portion is approached, said means being positioned in first side portion to increase the compressibility of said first side portion.

3. A support as set forth in claim 2 wherein said means comprises wall structure defining a cavity in said first side portion of the pad.

4. A support as set forth in claim 2 wherein said means comprises groove defining structure adjacent said rail in said first side portion of the pad.

5. A support as set forth in claim 1 wherein is included a metallic reinforcing plate in said pad, said plate including a projection extending outwardly from said first side portion and into juxtaposed relationship to the side of the rail adjacent said first side portion.

6. A support as set forth in claim 5 wherein said plate has a leg extending from said projection above at least a portion of the rail, said leg presenting a contact surface engageable with said rail and a fastener for the latter.

7. A support as set forth in claim 3 wherein said cavity is enclosed within the pad material.

References Cited UNITED STATES PATENTS 2,094,279 2/ 1937 Moses 238283 2,146,341 2/1939 Kahn 238-283 2,996,256 8/ 1961 Moses 238-283 3,189,279 6/1965 Horniblow et al 238283 FOREIGN PATENTS 211,494 11/ 1957 Australia.

933,342 9/1955 "Germany.

468,182 6/1937 Great Britain.

678,731 9/1952 Great Britain.

797,889 7/ 1958 Great Britain.

938,328 10/ 1963 Great Britain.

ARTHUR L. LA POINT, Prim ry Examiner.

R. A. BERTSCH, Assistant Examiner. 

